An electron multiplier can be formed by bonding a perforated or porous plate, e.g., a lead glass plate, between an input electrode and an output electrode, and providing a high voltage direct current (DC) field between the electrodes. When incident particles, such as electrons, ions, or photons, strike the input electrode and collide against glass surfaces within the plate, electrons, sometimes called “secondary electrons”, are produced. The secondary electrons are accelerated by the DC field toward the output electrode, and collide against other surfaces within the plate to produce more secondary electrons, which can in turn produce more electrons as they accelerate through the plate. As a result, an electron cascade or avalanche can be produced as the secondary electrons accelerate through the plate and collide against more surfaces, with each collision capable of increasing the number of secondary electrons. A relatively strong electron pulse can be detected at an output face.
Electron multipliers commonly include two types of plates: microchannel plates (MCPs) and microsphere plates (MSPs). Microchannel plates (MCPs) typically include a glass plate perforated with a regular, parallel array of microscopic channels, e.g., cylindrical and hollow channels. Each channel, which can serve as an independent electron multiplier, has an inner wall surface formed of a semi-conductive and electron emissive layer. As incident particles enter a channel and collide against the wall surface to produce secondary electrons, a cascade of electrons can be formed as the secondary electrons accelerate along the channel (due to the DC field), and collide against the wall surface farther along the channel, thereby increasing the number of secondary electrons.
Microsphere plates (MSPs) typically include a glass plate formed of microscopic glass spheres that have semi-conductive and electron emissive surfaces. The spheres are packed and bonded together, e.g., by compression and sintering. As incident particles collide against the surfaces of the spheres to form secondary electrons, a cascade of electrons can be formed as the secondary electrons accelerate through the interstices defined by the spheres and collide against the surfaces of other spheres.